Removing noise from a seismic measurement

Abstract

A technique includes spatially filtering a signal that is derived from a seismic acquisition. The filtering is associated with a filter length, and the filtering includes varying the filter length with frequency. The filtering may be used in connection with adaptive noise attenuation, which is applied to decomposed subbands. Furthermore, the filtering may be applied during the reconstruction of the signal from the subbands.

What is claimed is: 
     
       1. A method for conducting a seismic survey using a survey vessel comprising:
 acquiring a signal using a seismic streamer attached to the survey vessel, wherein acquiring the signal is performed using a multi-component sensor having particle motion sensing capabilities associated therewith; 
 decomposing, at the seismic streamer or onboard the survey vessel, the signal derived from a seismic acquisition into subbands in successive stages, the subbands being associated with at least different frequency ranges of the signal; 
 selectively applying, using a low pass spatial filter, at the seismic streamer or onboard the survey vessel, adaptive noise attenuation in between the successive stages such that the stages decompose noise-attenuated subbands, wherein the low pass spatial filter is configured to adjust a filter length based upon, at least in part, a frequency being filtered; and 
 reconstructing, at the seismic streamer or onboard the survey vessel, the signal from the subbands resulting from the decomposition. 
 
     
     
       2. The method of  claim 1 , wherein
 some of the subbands resulting from the decomposition are associated with lower frequencies than the remaining subbands resulting from the decomposition; and 
 the act of applying adaptive noise attenuation comprises applying the adaptive noise attenuation to the subbands that are associated with the lower frequencies and not applying adaptive noise attenuation to the remaining subbands. 
 
     
     
       3. The method of  claim 1 , wherein the subbands are further associated with different wavenumber ranges. 
     
     
       4. The method of  claim 3 , wherein
 some of the subbands resulting from the decomposition are associated with lower wavenumbers than the remaining subbands resulting from the decomposition; and 
 the act of applying adaptive noise attenuation comprises applying the adaptive noise attenuation to the subbands that are associated with the lower wavenumbers and not applying the adaptive noise attenuation to the remaining subbands. 
 
     
     
       5. The method of  claim 1 , wherein
 some of the subbands resulting from the decomposition are within a frequency-wavenumber region associated with a desired seismic signal; and 
 the act of applying adaptive noise attenuation comprises applying the adaptive noise attenuation to the subbands that are within the frequency-wavenumber region and not applying the adaptive noise attenuation to the first subbands that are outside of the frequency-wavenumber region. 
 
     
     
       6. The method of  claim 1 , wherein the act of decomposing comprises performing discrete wavelet transformations. 
     
     
       7. The method of  claim 1 , further comprising:
 spatially filtering the noise attenuated subbands; and 
 for each noise attenuated subband, regulating a length of the filtering based on a frequency associated with the noise attenuated subband. 
 
     
     
       8. The method of  claim 7 , wherein spatially filtering includes adapting the filtering to pass through aliasing components of the noise-attenuated subbands. 
     
     
       9. The method of  claim 1 , wherein decomposing the signal is performed prior to selectively applying adaptive noise attenuation and selectively applying adaptive noise attenuation is performed prior to reconstructing the signal. 
     
     
       10. A system for conducting a seismic survey using a survey vessel comprising:
 a seismic streamer attached to the survey vessel, the seismic streamer configured to acquire a signal using a multi-component sensor having particle motion sensing capabilities associated therewith; 
 an interface, at the seismic streamer or onboard the survey vessel, to receive data indicative of a signal derived from a seismic acquisition; and 
 a processor, at the seismic streamer or onboard the survey vessel, to:
 decompose the signal into subbands in successive stages, the subbands being associated with at least different frequency ranges of the signal; 
 selectively apply, using a low pass spatial filter, adaptive noise attenuation in between the successive stages such that the stages decompose noise-attenuated subbands, wherein the low pass spatial filter is configured to adjust a filter length based upon, at least in part, a frequency being filtered; and 
 reconstruct the signal from the subbands resulting from the decomposition. 
 
 
     
     
       11. The system of  claim 10 , wherein the processor is further adapted to selectively spatially filter the subbands between the stages and regulate a length of the filtering based on a frequency associated with the subband being filtered. 
     
     
       12. The system of  claim 10 , wherein
 some of the subbands resulting from the decomposition are associated with lower wavenumbers than the remaining subbands resulting from the decomposition, and 
 the processor is further adapted to process the data to apply the adaptive noise attenuation to the subbands that are associated with the lower wavenumbers and not apply the adaptive noise attenuation to the remaining subbands. 
 
     
     
       13. The system of  claim 10 , wherein
 some of the subbands resulting from the decomposition are within a frequency-wavenumber region associated with a desired seismic signal; and 
 the processor is further adapted to apply the adaptive noise attenuation to the subbands that are within the frequency-wavenumber region and not apply the adaptive noise attenuation to the subbands that are outside of the frequency-space region. 
 
     
     
       14. The system of  claim 10 , wherein the processor is further adapted to perform discrete wavelet transformations to decompose the signal. 
     
     
       15. The system of  claim 10 , further comprising:
 a spread of at least one streamer comprising seismic sensors to acquire data indicative of the signal derived from the seismic acquisition; and 
 a vessel to tow the spread.